A 45-year-old man has resistant hypertension despite four antihypertensive drugs. Serum potassium is 3.0 mmol/L. Plasma aldosterone is elevated with suppressed renin. What is the most appropriate next diagnostic step?
A
Start spironolactone immediately
B
CT scan of adrenal glands
C
Confirmatory aldosterone suppression test
D
Renal artery Doppler study